An ignition device typically includes a spark plug, for example, in the case of a spark-ignition internal combustion engine. The spark plug ignites an air-fuel mixture by means of an electrical spark. A multi-spark method of igniting the air-fuel mixture has been proposed in recent years, in which the ignition device ignites the air-fuel mixture by means of a multi-spark operation for every combustion stroke in order to improve a combustion state of the air-fuel mixture. During a period of the multi-spark operation, the spark plug repeatedly generates a spark.
In order to perform the multi-spark operation, an ignition control device requires information on a time when the multi-spark operation is started such as a spark timing and a period during which the multi-spark operation is performed such as a multi-spark period. The spark timing and the multi-spark period are, for example, determined by an engine control unit, an electronic control unit, or the like, any of which is referred to herein as the ECU, based on a driving state of the internal combustion engine. In the above-described case, the ignition control device requires receiving both a spark timing signal and a multi-spark period signal from the ECU, where the spark timing signal and the multi-spark period signal include information on the spark timing and the multi-spark period, respectively.
In a conventional case, such as is described in U.S. Patent Application Publication No. 2006/0021607, the ECU outputs the spark timing signal to the ignition control device, and then the ECU outputs the multi-spark period signal to the ignition control device. Consequently, after the spark plug starts generating a spark based on the spark timing signal, the spark plug performs the multi-spark operation during a predetermined period based on the multi-spark period signal. However, in advance of a time when the spark plug starts generating a spark, the ignition control device can not recognize an expected energy consumption or an energy density during the multi-spark operation. Therefore, an amount of energy sufficient to cover all relevant conditions is necessarily supplied to an ignition coil from an electrical energy generator whether the conditions are likely or unlikely. By covering all of the relevant conditions, a large energy is supplied regardless of an ignition condition, and a negative influence on fuel-efficiency is caused.